Potassium-ion　batteries　have　drawn　great　attention　owing　to　the　abundant　and　low-cost　potassium　resources.　However,　the　lack　of　highly　reversible　K+-storage　electrodes　remains　a　key　concern,　due　to　the　large　size　of　K+　ions.　Inorganic-open-framework　KTiOPO4-type　(KTP)　anodes　are　promising　K+-hosts,　due　to　their　large　interstitial　vacancies　allowing　fast　and　reversible　insertion　of　K+　ions　with　low　structural　evolution.　Here,　we　report　a　new　member　in　the　KTP　family,　K0.63Cr0.56Ti0.55OPO4　(KCTP),　with　partial　aliovalent　substitution.　The　KCTP　exhibits　a　high　specific　capacity　of　123.4　mAh/g　and　achieves　stable　cycle　life,　over　135　days　with　98%　capacity　retention　at　10　mA/g　and　up　to　9.9　months　with　81%　retention　at　20　mA/g.　The　K+-storage　process　involves　biphasic　reaction　and　solid-solution　reaction,　with　a　minor　volume　change　of　only　8.06%.　This　work　demonstrates　that　inorganic　open　frameworks　with　aliovalent　substitution　may　open　a　promising　way　to　design　high-performance　potassium-ion　batteries.